Ohnesorge et al, U.S. Pat. No. 4,422,335 discloses a pressure transducer made using quartz plates and Bernot, U.S. Pat. No. 5,189,591 discloses a pressure transducer using glass plates. Whether glass or quartz, these sensors have generally been mounted to headers made of aluminum or stainless steel. Besides being expensive to machine, another disadvantage to these aluminum and stainless steel headers is that it is difficult to hermetically seal the electrical connections to these sensors. Without a hermetic seal liquid and gas contaminants in the sensing medium can enter and ruin the sensor. As a result these types of sensors can only be used where the pressure medium is contaminant free such as dry gasses.
Accordingly, a need exists for a more robust capacitance sensor where the electrical connections can be hermetically sealed.